When it is desired to cut a steel plate or the like with use of a laser-beam processing machine, it has been conventionally common practice to converge a laser beam upon or in the vicinity of the front surface of a material to be cut and to set the pressure of an assist gas at such a relatively low level that does not exceed 6 Kg/cm.sup.2.
In the case of cutting the steel plate or the like using the conventional laser-beam processing apparatus, there has not occured no special problem; whereas, in the case of cutting such a material having a high melting point and a high relfection factor as aluminum or copper using the same apparatus, it has been impossible to obtain good cut results.
More specifically, when it is desired to cut such a high melting-point and reflection-factor material as aluminum or copper with use of the conventional laser-beam processing machine, there has occurred such a disadvantage that a part or so called dross of the cutting material melted during the cutting operation will be abruptly cooled during its flow from the front side of the material to the rear side thereof and accordingly be increased in viscocity, which results in that the dross adheres to the rear face of the cutting material, thus disadvantageously involving the imcompleted cutting of the material or providing a rough cut surface thereto due to the dross.
In addition, the prior art laser-beam processing machine has had such a problem that, when it is desired to process a material of a high reflection factor with use of such a prior art machine, part of a laser beam reflected on the high-reflection-factor material enters a laser oscillator part, which sometimes causes the damage of the laser oscillator.
In view of such defects in the prior art as mentioned above, it is an object of the present invention to provide a laser-beam cutting method and system which can sharply and finely cut such materials having high melting points and high reflection factors such as aluminum or copper with use of a laser beam.